The present invention relates to coated display pieces and the method of producing them and, more particularly, to windows for electronic and mechanical displays which have been coated with a coating material layer.
Electronic displays are devices used to exhibit electronically generated graphical and textual images. There are many different types of electronic displays, and many more are being developed. Among the more familiar types of electronic displays are: liquid crystal displays (“LCDs”); cathode ray tubes (“CRTs”); arrays of light-emitting diodes (“LEDs”) or organic light-emitting diodes (“OLEDs”); plasma display panels (“PDP”); field emission displays (“FED”); and electroluminescent (“EL”) displays. LCDs and EL displays are particularly useful in portable electronic devices due to their light weight and low power consumption relative to other display technologies.
Electronic and mechanical displays are used in a wide variety of products, including, but not limited to, cellular telephones; digital and analog watches; sports computers; monitors; electronic and mechanical displays for gauges, such as meters, liquid level indicators, pedometers, speedometers, odometers, tachometers, and the like; photographic devices, such as digital or film cameras, either still or video, light meters, electronic flash units, spectrometers, and the like; metrology devices, such as volt-ohm-millimeters, automotive diagnostic devices, telecommunications service devices, and the like; financial transaction devices, such as barcode scanners, automated teller machines, cash registers, and other scanning devices; security devices, such as retina scanners, fingerprint readers, and other biometric devices; and portable digital assistants (PDAs).
One option for windows for display devices is glass because it meets requirements for optical clarity and flatness, and it has good gas and moisture barrier properties and good electrical, mechanical, thermal, and chemical resistance properties. One advantage of glass is that, for a given plate thickness, it is less flexible than plastic, and so it can be much thinner than a plastic window of equal rigidity, and therefore it can be located closer to the display behind the window, allowing the product to be thinner. However, glass has a disadvantage in that it is more brittle than most common plastics, and is subject to breakage that can produce loose fragments. It is therefore of limited usefulness in many applications. Various plastics have been proposed as replacements for glass, often because they are lighter weight and more resistant to breakage than glass. Displays made with such plastic materials have been under development for years, but plastics have limitations which interfere with their performance. These limitations include unsatisfactory optical quality, flatness, scratch resistance, solvent resistance, thermal resistance, and liquid and gas barrier properties.
It is known to coat glass windows to protect them from breakage and environmental damage. Tough, thermoset polyurethane coatings and films exemplify one type of external transparent coating that has been used to protect glass from particle erosion, abrasion and breakage. See, for example, U.S. Pat. No. 5,939,188, which discusses such coatings and proposes an improved multilayer coating system which is said to be useful in aircraft transparencies or as windows for military ground vehicles. However, such multilayer coating systems are complex and require multiple deposition steps.
It is also known to coat glass containers with a layer of plastic, such as polyurethane, to prevent those containers, such as soft drink bottles, from shattering on impact. Thus, Waugh U.S. Pat. Nos. 4,092,953 and 4,225,638 disclose a method and apparatus for coating a glass container with a layer of plastic by rotating the container about its horizontal axis while a plurality of liquid applicator nozzles supply uncured plastic liquid to associated areas on the container. The container is also rotated during the subsequent curing of the plastic. However, such a system is only useful on cylindrical objects which can be rotated about a horizontal axis.
US Published Patent Applications 200401052693 and 20040106707 describe a method of pad printing a coating on an optical surface of an optical device. The coating includes at least one adhesion promoter selected from the group consisting of glycol ethers, glycol ether acetates, benzotriazole, a silane, and combinations thereof. It can also include at least one polymerizable material, and at least one polymerization initiator. The adhesion promoter is described as chemically etching, softening, or reacting with the outer surface of a substrate. However, the use of such an adhesion promoter complicates the coating formulation.
Accordingly, the need remains for coated display pieces and for a method of coating display pieces such as window displays for electronic and mechanical devices with a protective layer.